1. Field of the Invention
The present invention relates generally to a method for manufacturing electrically-conductive tips which are used in components of vacuum micro-electronic devices.
2. Description of the Related Art
Electrically-conductive tips having small dimensions for use in vacuum micro-electronic components generally have a pyramid shape and are of a height of approximately 1 .mu.m and a base area of approximately 1.times.1 .mu.m.sup.2. Such electrically-conductive tips are used as a tunnel tips and are generally manufactured of doped silicon.
A known technique for the manufacture of electrically-conductive tips utilizes micro-mechanics, as disclosed in, for example, the publication by Heuberger, MIKROMECHANIK, Springer Verlag, pp. 426-428. For instance, the electrically-conductive tips are manufactured by anisotropic etching which is dependent on crystal orientation. To that end, a silicon wafer having a corresponding crystal orientation is provided with an oxide mask that includes a matrix of circular silicon oxide spots. By under-etching in the anisotropic etching step, pyramids having cone angle of approximately 70.degree. are formed under the silicon oxide spots.
The Heuberger publication also discloses a method in which a conductive tip of metal can be manufactured. A mask having circular openings is formed on a silicon substrate. Pyramidal metal islands form inside the openings as a result of vapor-deposition of molybdenum that is directed in the direction of the normal to the surface and perpendicular to the surface and as the result of rotation of the silicon substrate. Further mask steps or hybrid technologies are required using known methods to manufacture a complete component from the, thus, form conductive tip.
German patent 40 41 276 discloses an electrically-conductive tip of doped silicon which is manufactured by selective epitaxy. A mask is provided with an opening so that the surface of the substrate is uncovered. An electrically conductive tip is produced on the uncovered surface by selective epitaxy wherein the layer growth in the direction parallel to the surface of the substrate is less than in the direction perpendicular to the surface of the substrate. As soon as the height of the tip is no more than one half the clearance of the opening, a punctiform tip arises using this method. The height of the tip is dependent on the dimensions of the opening of the mask.